The invention relates to a steerable mole for making a hole in the ground, which drilling mole has a round tubular body, a guidable drilling instrument mounted in front on this body by means of a ball and socket joint and means mounted in the body in order to guide the drilling instrument in relation to the body.
A steerable drilling mole of this sort is described in the Belgian patent no. 906 079 to the name of Nik Smet. In this known drilling mole the drilling instrument is formed by a head which is provided with one or more spraying devices for liquid under high pressure. The means for guiding this drilling instrument in relation to the tubular body are formed by three or more cylinder-piston mechanisms which are arranged around the geometric axis in the body. Cylinder-piston mechanisms are relatively expensive. The setting or adjusting of the correct direction of the drilling instrument with assistance of these cylinder-piston mechanisms is not always simple.